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NVD / CVE Program· CNA redhat

CVE-2021-3981: A flaw in grub2 was found where its configuration file, known as grub.cfg, is being created with the wrong permission set allowing non…

Noroxi assessment

Priority: Monitor (action score 13/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.31% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: grub2-common (AlmaLinux:8) 1:2.02-123.el8.alma; grub2-efi-aa64 (AlmaLinux:8) 1:2.02-123.el8.alma; grub2-efi-aa64-cdboot (AlmaLinux:8) 1:2.02-123.el8.alma.

Low priority for now. Upgrade to grub2-common (AlmaLinux:8) 1:2.02-123.el8.alma; grub2-efi-aa64 (AlmaLinux:8) 1:2.02-123.el8.alma; grub2-efi-aa64-cdboot (AlmaLinux:8) 1:2.02-123.el8.alma or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

A flaw in grub2 was found where its configuration file, known as grub.cfg, is being created with the wrong permission set allowing non privileged users to read its content. This represents a low severity confidentiality issue, as those users can eventually read any encrypted passwords present in grub.cfg. This flaw affects grub2 2.06 and previous versions. This issue has been fixed in grub upstream but no version with the fix is currently released.

LowCVSS 3.3 · v3.1—No exploit Fix available
Published
Mar 10, 2022
Updated
Jun 17, 2026
EPSS
0.3% · 25th percentile

Report tools

JSON

Action score

13

Monitor

Low priority for now.

CVSS
13 / 40 · 3.3 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.3%

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  • A fix has been released

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  • when exploit code appears or is weaponized
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Noroxi analysis

What does it mean in your environment?

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
gnugrub2
fedoraprojectfedora

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • fedoraproject fedora34
  • gnu grub2up to 2.06 inclusive

Versions reported by the vendor

Affected version ranges reported by the assigning authority (redhat). Independent of NVD's CPE analysis and usually ahead of it.

  • n/a grub2

    • grub2 2.06 and previous versionsaffected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:8grub2-commonbefore 1:2.02-123.el8.alma1:2.02-123.el8.alma
AlmaLinux:8grub2-efi-aa64before 1:2.02-123.el8.alma1:2.02-123.el8.alma
AlmaLinux:8grub2-efi-aa64-cdbootbefore 1:2.02-123.el8.alma1:2.02-123.el8.alma
AlmaLinux:8grub2-efi-aa64-modulesbefore 1:2.02-123.el8.alma1:2.02-123.el8.alma
AlmaLinux:8grub2-efi-ia32before 1:2.02-123.el8.alma1:2.02-123.el8.alma
AlmaLinux:8grub2-efi-ia32-cdbootbefore 1:2.02-123.el8.alma1:2.02-123.el8.alma
AlmaLinux:8grub2-efi-ia32-modulesbefore 1:2.02-123.el8.alma1:2.02-123.el8.alma
AlmaLinux:8grub2-efi-x64before 1:2.02-123.el8.alma1:2.02-123.el8.alma
AlmaLinux:8grub2-efi-x64-cdbootbefore 1:2.02-123.el8.alma1:2.02-123.el8.alma
AlmaLinux:8grub2-efi-x64-modulesbefore 1:2.02-123.el8.alma1:2.02-123.el8.alma
AlmaLinux:8grub2-pcbefore 1:2.02-123.el8.alma1:2.02-123.el8.alma
AlmaLinux:8grub2-pc-modulesbefore 1:2.02-123.el8.alma1:2.02-123.el8.alma
AlmaLinux:8grub2-ppc64lebefore 1:2.02-123.el8_6.8.alma1:2.02-123.el8_6.8.alma
AlmaLinux:8grub2-ppc64le-modulesbefore 1:2.02-123.el8.alma1:2.02-123.el8.alma
AlmaLinux:8grub2-toolsbefore 1:2.02-123.el8.alma1:2.02-123.el8.alma
AlmaLinux:8grub2-tools-efibefore 1:2.02-123.el8.alma1:2.02-123.el8.alma
AlmaLinux:8grub2-tools-extrabefore 1:2.02-123.el8.alma1:2.02-123.el8.alma
AlmaLinux:8grub2-tools-minimalbefore 1:2.02-123.el8.alma1:2.02-123.el8.alma
Debian:12grub2before 2.06-82.06-8
openSUSE:Tumbleweedgrub2before 2.06-13.12.06-13.1
Red Hat:enterprise_linux:8::baseosgrub2before 1:2.02-123.el81:2.02-123.el8
Red Hat:enterprise_linux:8::baseosgrub2-commonbefore 1:2.02-123.el81:2.02-123.el8
Red Hat:enterprise_linux:8::baseosgrub2-debuginfobefore 1:2.02-123.el81:2.02-123.el8
Red Hat:enterprise_linux:8::baseosgrub2-debugsourcebefore 1:2.02-123.el81:2.02-123.el8

+22

Same product

gnu: all records

Other highest-scoring records for the same primary product.

  • CVE-2024-56737GNU GRUB (aka GRUB2) through 2.12 has a heap-based buffer overflow in fs/hfs.c via crafted sblock data in an HFS filesystem.
    35Monitor
  • CVE-2022-2601A buffer overflow was found in grub_font_construct_glyph().
    34Monitor
  • CVE-2020-10713A flaw was found in grub2, prior to version 2.06.
    33Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2021-20233Mar 3, 2021 · A flaw was found in grub2 in versions prior to 2.06.
    32Monitor
  • ← EarlierCVE-2021-3418Mar 15, 2021 · If certificates that signed grub are installed into db, grub can be booted directly.
    25Monitor
  • Later →CVE-2021-3695Jul 6, 2022 · A crafted 16-bit grayscale PNG image may lead to a out-of-bounds write in the heap area.
    18Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
almalinux:grub2-common1:2.02-123.el8.alma · AlmaLinux:8Package registry (OSV)
almalinux:grub2-efi-aa641:2.02-123.el8.alma · AlmaLinux:8Package registry (OSV)
almalinux:grub2-efi-aa64-cdboot1:2.02-123.el8.alma · AlmaLinux:8Package registry (OSV)
almalinux:grub2-efi-aa64-modules1:2.02-123.el8.alma · AlmaLinux:8Package registry (OSV)
almalinux:grub2-efi-ia321:2.02-123.el8.alma · AlmaLinux:8Package registry (OSV)
almalinux:grub2-efi-ia32-cdboot1:2.02-123.el8.alma · AlmaLinux:8Package registry (OSV)
almalinux:grub2-efi-ia32-modules1:2.02-123.el8.alma · AlmaLinux:8Package registry (OSV)
almalinux:grub2-efi-x641:2.02-123.el8.alma · AlmaLinux:8Package registry (OSV)
almalinux:grub2-efi-x64-cdboot1:2.02-123.el8.alma · AlmaLinux:8Package registry (OSV)
almalinux:grub2-efi-x64-modules1:2.02-123.el8.alma · AlmaLinux:8Package registry (OSV)
almalinux:grub2-pc1:2.02-123.el8.alma · AlmaLinux:8Package registry (OSV)
almalinux:grub2-pc-modules1:2.02-123.el8.alma · AlmaLinux:8Package registry (OSV)
debian:grub22.06-8 · Debian:12Package registry (OSV)
opensuse:grub22.06-13.1 · openSUSE:TumbleweedPackage registry (OSV)
red hat:grub21:2.02-123.el8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:grub2-common1:2.02-123.el8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:grub2-debuginfo1:2.02-123.el8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:grub2-debugsource1:2.02-123.el8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:grub2-efi-aa641:2.02-123.el8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:grub2-efi-aa64-cdboot1:2.02-123.el8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:grub2-efi-aa64-modules1:2.02-123.el8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:grub2-efi-ia321:2.02-123.el8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:grub2-efi-ia32-cdboot1:2.02-123.el8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:grub2-efi-ia32-modules1:2.02-123.el8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:grub2-efi-x641:2.02-123.el8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:grub2-efi-x64-cdboot1:2.02-123.el8 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
rocky linux:grub21:2.02-123.el8 · Rocky Linux:8Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
low · data can be read
Integrity
none
Availability
none
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
Low
Integrity impact
None
Availability impact
None

Weakness class (CWE)

CWE-276 · Incorrect Default Permissions

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (3 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records